1. Field of the Invention
The present invention relates to a process for manufacturing a hollow blade for a turbo-machine.
The advantages stemming from the use of large chord blades for turbo-machines have become apparent, particularly in the case of the fan rotor blades of bypass turbojet engines. These blades must meet severe conditions of use and, in particular, must possess satisfactory mechanical characteristics associated with anti-vibration properties and the ability to withstand impact from foreign bodies. Furthermore, in order to achieve sufficient speeds at the tips of the blades they are generally made hollow so as to keep the mass as low as possible.
2. Summary of the Prior Art
EP-A-0 500 458 describes a process for the manufacture of a hollow blade for a turbo-machine, particularly a large chord blade for a fan rotor. The primary blade parts utilized in this process comprise two outer metal sheets and at least one central metal sheet. The process described includes a hot-forming operation with bending and twisting of the parts, a diffusion welding operation in specific areas, and an inflation operation using pressurised gas inducing a superplastic shaping bringing the outer surfaces of the blade to the desired profile. Suitable tools, particularly shaping dies, are used for carrying out these operations.
It is an object of the invention to improve this and the numerous other known processes for the manufacture of hollow blades, with a view to obtaining blades with improved mechanical characteristics optimized for the conditions of use, while ensuring repeatability of quality and ease of manufacture at low cost.